Quick config snippet to setup external NTP server to synchronize time on Cisco IOS router.
labisr-01(config)#ip name-server 4.2.2.2
labisr-01(config)#ntp server 0.europe.pool.ntp.org
Translating "0.europe.pool.ntp.org"...domain server (4.2.2.2) [OK]
labisr-01(config)#clock timezone GMT 0
labisr-01(config)#
Please note that first I setup nameserver on router to be able to resolve NTP server FQDN.
Once NTP server is set we can check status of it:
labisr-01#sh ntp associations
address ref clock st when poll reach delay offset disp
*~88.191.227.26 82.197.188.130 3 37 64 377 38.7 2.04 1.4
* master (synced), # master (unsynced), + selected, - candidate, ~ configured
labisr-01#
labisr-01#sh ntp status
Clock is synchronized, stratum 4, reference is 88.191.227.26
nominal freq is 250.0000 Hz, actual freq is 250.0000 Hz, precision is 2**18
reference time is D442C30E.7A93ED17 (22:58:22.478 GMT Mon Nov 5 2012)
clock offset is 2.0449 msec, root delay is 71.69 msec
root dispersion is 61.25 msec, peer dispersion is 1.36 msec
labisr-01#